A new attempt, this time with what I think is quite a strong story attached. My main concern is that something like this will have been done before.

An isolated beach experienced some sort of chemical spill. During the cleanup effort someone noticed markings in the sand and footprints that couldn't be accounted for. Via various agencies and bureaucratic processes this eventually came to the notice of the Foundation who took over the cleanup and isolated the beach, using the chemical spill as a cover.

It was discovered that not only footprints but other signs of human activity were present, including scorch marks on the sand which would appear and grow as if a fire was lit. Occasionally writing would appear on the sand along the lines of 'Who are you?', 'Where are you?' and 'Wait for me.' When a researcher wrote a reply in the sand, a dialogue was started and the story started to come out.

The footprints and other markings are the traces of a solitary human presence who believed/s that he was the last person left alive (possibly after an XK class scenario, possibly after a mysterious event, or possibly just after inexplicably waking up with everyone else gone). He claims to have been alone for a long time and clings desperately to these traces of human contact after so long alone. There's no immediate physical danger to the guy where he is, just that there are no other humans around and this one beach is the only place he's seen any signs of them.

I have some ideas about what led up to this and the cause behind it:
- The Foundation activated one of their reality restructuring contingencies after an XK event and this one person was somehow left behind. This would mean that the world he's in has been heavily impacted by the event, and might mean more danger to him than I really want (the story isn't about his struggle to survive physical danger, just how someone might react to being the last person left and suddenly receiving some sort of contact).
- Something took a liking to him and pulled him to one side to keep him as a pet, somewhat like a solo goldfish in a bowl.
- He's responsible for it himself, possibly even an ex-Foundation researcher who was involved in a test or activated something that led to his being here. This would raise the risk factor for the Foundation as his knowledge (even degraded after years alone) would be a security breach if he communicated with anyone else. If he had an especially high clearance it might even mean that the Foundation takes active measures to prevent lower level employees from interacting with the beach for fear of an internal security breach - meaning that not only is he alone, but his chance of any sort of communication with other humans is limited or non-existent.

I'm thinking that by the time there's any contact his tone will be, at best, distant. He's had long enough to accept his fate, come to terms with it. There's no actual danger to him and he probably believes - in a very calm, collected manner - that he's gone mad and is either writing the other messages himself or simply hallucinating them in order to stay sane.

The only alternative to that Ican see would be desperation, which would be more the case if the guy is a security risk himself. The Foundation would then be duty-bound to prevent interaction with him and any messages would become increasingly desperate, promising the world for nothing more than a 'hello' written back to him.

Edit: I can see the similarity to 1171,but I think if anything the idea is opposite. 1171 works from being alien, but identifiable. The idea here is that the scip is completely human, but without any other humans, or other sapient lifeforms, around. I just have a mental image of someone standing on this isolated beach, staring out to sea, hoping for some sign of human life.